my water level is right under the black trim of the tank... my overflow box is at as low as it can go.. I guess I should put more water.. I heard that It's only advisable to put water where I have it now.. but I can't do that with this overflow. hmmm
OK...I got you now. I thought everything was already running, but by your other threads I see you are still setting everything up.
The water line on my tank is slightly above the trim on top. You can add more water so the water line is higher and then set your overflow.
2 u-tubes or 3 or 4...they won't increase your flow unless you also increase the size of the bulkhead on the drain side of the overflow. If you have a 1.5" bulkhead, and 2 1.25" u-tubes, they will be restricted by the smaller size of the bulkhead.